Use jquery-ui-{{this.pkg.version}}.zip as quick download (obs: without '.custom.` )
Replace `npm install && npm update` with `npm prune && npm install`

- `update` has been removed, because we are not using repo packages anymore;
- `prune` has been added. So, extraneous packages are removed before the
  installation. Otherwise, former requirements could fail the latter. Eg.
  extraneous left by jquery-ui 1.10.2 is not satisfied by a subsequent npm
  installation on jquery-ui 1.9.2;
1.10.2-2